In the northern parts of the United States, dairy cattle are confined in dairy farms and fed with phosphate-rich feed during the long winter periods. During this long period of confinement, that lasts from the early fall until the early spring, the “in barn” produced manure accumulates in the farm. Similarly, poultry-based farms produce different but sometimes more concentrated manure. The concentrated manure from the dairy farms, the poultry farms or any other type of animal farms is usually stored outside of the barn in a manure pit and then spread over the fields in the spring. Government agencies have recommended this practice of spreading of manure over fields during spring as a method of disposing of agricultural waste while fertilizing the ground. This practice has led to purchase, maintenance and paying of taxes on land that is kept primarily for manure overspread, which is a major financial burden for the farmers.
Manure is composed of 96% water and of 4% solid nutrient materials. In other words, unprocessed manure is a very dilute source of fertilizing nutrients. Furthermore, studies have shown that phosphorous and other nutrients present in manure are water soluble, which causes these nutrients to be washed out by rain or snow. Therefore one ton of manure yields only 7 to 10 pounds of nutrients to the ground.
Spreading of manure is not allowed during the winter months on top of snow to prevent runoff of phosphates and other contaminants to nearby rivers, lakes and other groundwater systems with the melting of the snow. However, the process of spreading of the concentrated manure in the spring still causes excess runoff of phosphates and other contaminants to nearby rivers, lakes and other groundwater systems. Agricultural runoff, rich in nutrients like phosphorus and nitrogen has been linked to toxic microorganisms. These microorganisms are known to kill and/or cause diseases in fish and other animals and pose a serious health risk to humans.
Typical dairy manure contains nitrogen (N) and phosphorous (P) at a ratio of 3 to 1. The optimum fertilizer ratio of N:P for growing corn is 8 to 1. Therefore, the farmer has to spread in addition to the manure a large amount of urea for adding nitrogen in order to generate the required 8 to 1 ratio of N:P in the ground. Other plants require different ratios of N:P and the amount and type of additives need to be modified accordingly. This process of adding and spreading urea or other additives increases both the labor and material cost of farming and requires that the farmer goes out in the fields several times during the year.
As was mentioned above, phosphorus is water soluble which leads to phosphorus being washed out from the manure pit and soil by rain and carried to rivers, lakes and other groundwater systems, thereby causing pollution and reducing the fertilizing value of the manure. Also, nitrogen evaporates from the manure pit as ammonia which generates undesirable odors and causes the concentration of insects and vermin, while again reducing the fertilizing value of the manure.
Several prior art methods have been suggested for treating manure on the barn site and for converting manure to fertilizer. However, most of the prior art methods are not efficient, not scalable, or not economical and may require the addition of other chemicals for producing fertilizer.
Accordingly, there is a need for an efficient, scalable, economically viable and environmentally friendly process for treating manure and for producing stable custom fertilizer without the need to add chemicals.